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Noise: an enemy to be dealt with and a major factor limiting communication system performance. However, what if there is gold in that garbage? In conventional engineering, our focus is primarily on eliminating, suppressing, combating, or even ignoring noise and its detrimental impacts. Conversely, could we exploit it similarly to biology, which utilizes noise‐alike carrier signals to convey information? In this context, the utilization of noise, or noise‐alike signals in general, has been put forward as a means to realize unconditionally secure communication systems in the future. In this tutorial article, we begin by tracing the origins of thermal noise‐based communication and highlighting one of its significant applications for ensuring unconditionally secure networks: the Kirchhoff‐law‐Johnson‐noise (KLJN) secure key exchange scheme. We then delve into the inherent challenges tied to secure communication and discuss the imperative need for physics‐based key distribution schemes in pursuit of unconditional security. Concurrently, we provide a concise overview of quantum key distribution schemes and draw comparisons with their KLJN‐based counterparts. Finally, extending beyond wired communication loops, we explore the transmission of noise signals over‐the‐air and evaluate their potential for stealth and secure wireless communication systems. [ABSTRACT FROM AUTHOR]

The rapid advancement of internet technology has raised attention to the importance of electronic voting in maintaining democracy and fairness in elections. E-voting refers to the use of electronic technology to facilitate the casting and counting of votes in elections. The need for designated verification arises from concerns about voter privacy, auditability, and the prevention of manipulation. Traditional e-voting systems use cryptographic techniques for security but lack verifiable proof of integrity. Integrating e-voting with a quantum designated verifier could address these challenges by leveraging the principles of quantum mechanics to enhance security and trustworthiness. In light of this, we propose a quantum e-voting scheme that uses a designated verifier signature. To ensure the confidentiality and authenticity of the voting process, the scheme uses quantum features like the no-cloning theorem and quantum key distribution. The proposed scheme has security properties like source hiding, non-transferability, and message anonymity. The proposed scheme is resistant to many quantum attacks, such as eavesdropping and impersonation. Due to designated verification, the scheme minimizes the risk of tempering. This paper provides a detailed description of the proposed scheme and analyzes its security properties. Therefore, the proposed scheme is efficient, practical, and secure. [ABSTRACT FROM AUTHOR]

Unconditional security for smart grids is defined. Cryptanalyses of the watermarked security of smart grids indicate that watermarking cannot guarantee unconditional security unless the communication within the grid system is unconditionally secure. The successful attack against the dynamically watermarked smart grid remains valid even with the presence of internal noise from the grid. An open question arises if unconditionally authenticated secure communications within the grid, together with tamper resistance of the critical elements, are satisfactory conditions to provide unconditional security for the grid operation. [ABSTRACT FROM AUTHOR]

Abstract Noise: an enemy to be dealt with and a major factor limiting communication system performance. However, what if there is gold in that garbage? In conventional engineering, our focus is primarily on eliminating, suppressing, combating, or even ignoring noise and its detrimental impacts. Conversely, could we exploit it similarly to biology, which utilizes noise‐alike carrier signals to convey information? In this context, the utilization of noise, or noise‐alike signals in general, has been put forward as a means to realize unconditionally secure communication systems in the future. In this tutorial article, we begin by tracing the origins of thermal noise‐based communication and highlighting one of its significant applications for ensuring unconditionally secure networks: the Kirchhoff‐law‐Johnson‐noise (KLJN) secure key exchange scheme. We then delve into the inherent challenges tied to secure communication and discuss the imperative need for physics‐based key distribution schemes in pursuit of unconditional security. Concurrently, we provide a concise overview of quantum key distribution schemes and draw comparisons with their KLJN‐based counterparts. Finally, extending beyond wired communication loops, we explore the transmission of noise signals over‐the‐air and evaluate their potential for stealth and secure wireless communication systems.

Commitment scheme is a fundamental cryptographic primitive that serve as building blocks for many other two-party protocols. In this paper, we propose a novel quantum bit commitment scheme, which is secure and does not require quantum memory. Our scheme processes the quantum information using coherent states and unambiguous state discrimination (USD) measurements, which can be experimentally realized by linear optics and photon detectors. We ensure the unconditionally hiding and binding property by preventing both Alice and Bob from obtaining complete information about the commitment in committing stage, and eliminate the requirement for quantum memory by performing USD measurements and phase shifts immediately after receiving the coherent states. [ABSTRACT FROM AUTHOR]

Most prior semi-quantum key distribution (SQKD) protocols are designed in the context of qubits. In this paper, we proposed an SQKD protocol using (d +1) quantum states in two mutually unbiased bases in the context of qudits without invoking the classical party's measurement capability. It not only decreases the quantum states sent by quantum party by half, but also improves the efficiency of key rate than qubits do. To prove the security of present protocol, we first illustrate that the present protocol is completely robust, and then prove its unconditional security from information theoretical perspective by computing its key rate and noise tolerance against cloning-based individual attack. The unconditional security proof demonstrates that the higher dimension of quantum system is, the higher key rate can be obtained and the higher noise tolerance is allowed in depolarization channel. [ABSTRACT FROM AUTHOR]

The rapid advancement of internet technology has raised attention to the importance of electronic voting in maintaining democracy and fairness in elections. E-voting refers to the use of electronic technology to facilitate the casting and counting of votes in elections. The need for designated verification arises from concerns about voter privacy, auditability, and the prevention of manipulation. Traditional e-voting systems use cryptographic techniques for security but lack verifiable proof of integrity. Integrating e-voting with a quantum designated verifier could address these challenges by leveraging the principles of quantum mechanics to enhance security and trustworthiness. In light of this, we propose a quantum e-voting scheme that uses a designated verifier signature. To ensure the confidentiality and authenticity of the voting process, the scheme uses quantum features like the no-cloning theorem and quantum key distribution. The proposed scheme has security properties like source hiding, non-transferability, and message anonymity. The proposed scheme is resistant to many quantum attacks, such as eavesdropping and impersonation. Due to designated verification, the scheme minimizes the risk of tempering. This paper provides a detailed description of the proposed scheme and analyzes its security properties. Therefore, the proposed scheme is efficient, practical, and secure.

In this paper, we prove the unconditional security of a single-state circular mediated semi-quantum key distribution protocol. It starts with a third-party quantum server, TP, sending a string of qubits sequentially through two classical users Alice and Bob, and finally back to TP. We derive an expression for the key rate in the asymptotic scenario. When the communication parties Alice and Bob observe that the error rate is less than a determined threshold, the key rate is always greater than 0, so they can distill a string of secure secret keys. At the end of this paper, we extend this protocol to the multiple users case, where more than two classical users establish a string of security keys. [ABSTRACT FROM AUTHOR]

In this paper, we design unconditionally secure multi-party computation (MPC) protocols in the asynchronous communication setting with optimal resilience. Our protocols are secure against a computationally unbounded malicious adversary characterized by an adversary structure Z , which enumerates all possible subsets of potentially corrupt parties. We present protocols with both perfect-security, as well as with statistical-security. While the protocols in the former class achieve all the security properties in an error-free fashion, the protocols belonging to the latter category achieve all the security properties except with a negligible error. Our perfectly secure protocol incurs an amortized communication of O (| Z | 2) bits per multiplication. This improves upon the protocol of Choudhury and Pappu (INDOCRYPT 2020) with the least known amortized communication complexity of O (| Z | 3) bits per multiplication. On the other hand, our statistically secure protocol incurs an amortized communication of O (| Z |) bits per multiplication. This is the first statistically secure asynchronous MPC protocol against general adversaries. Previously, perfectly secure and statistically secure MPC with an amortized communication cost of O (| Z | 2) and O (| Z |) bits, respectively, per multiplication was known only in the relatively simpler synchronous communication setting (Hirt and Tschudi in ASIACRYPT, Springer, 2013). [ABSTRACT FROM AUTHOR]

We consider in this work a physical layer authentication method in which a message authentication code, referred to as a tag, is transmitted along with the data message to provide a robust authentication method. This work diverges from previous work in the area when it comes to the tag generation method. While the previous works use methods based on cryptographic hash functions, our system employs unidimensional chaotic maps to generate these tags. Due to the loss of information about the initial condition of chaotic maps, we show that they are strong candidates for the tag generation process. We employ an information-theoretic approach to show that chaotic tags provide a positive lower bound on the unconditional security of the system even in a noiseless environment. To the best of our knowledge this is the first work where unconditional security is obtained independently of the noise power. Additionally, we calculate the probability of success for two active attacks to the authentication system: impersonation, substitution.

In order to construct unconditionally secure one-vote veto protocol, a primitive protocol of secure multiparty computations was defined, i.e., secure multiparty disjunction.Furthermore, by introducing a quantum cloud, a quantum secure multiparty disjunction (QSMD) protocol was proposed.BB84 states were took as quantum resources and only single-photon operations and measurements were needed.To avoid the flaws of infeasibility, i.e., most of existing quantum voting protocols need to perform operations and measurements in high-dimensional Hilbert space, a quantum anonymous one-vote veto protocol with a quantum cloud (QAOVC) was designed by using the QSMD protocol.In addition, to decentralize, a quantum anonymous one-vote veto (QAOV) protocol without any third party was presented.Compared with related protocols, the proposed protocols require less quantum resources and simpler operations, so they have better feasibility.Under the semi-honest model, quantum perfect encryption and classical one-time pad can ensure the unconditional security of the proposed protocols, i.e., it can completely meet secure requirements of one-vote veto and perfectly protect the privacy of the voters.Finally, simulation experiments are implemented on IBM Qiskit, and the experimental results show that the protocols are correct and feasible.

Unconditional security means that knowledge of an encrypted text does not provide any information about the corresponding plaintext: or more. regardless of the number of ciphertexts available to an attacker. no amount of cryptanalysis can break the cipher. Until now. only the One-Time Pad (OTP) method meets this condition with well-defined assumptions. The design of a Homomorphic Encryption scheme that allows operations over the encrypted data is required in current applications to reach the highest possible level of privacy. However. existing symmetric solutions that use OTP have a key management problem: they are not linear encryption. which means that they have high computational complexity. and some of them do not meet all homomorphic properties. This article simulates the 0TP taking into consideration these issues and achieving the maximum resistance to cryptanalysis, even when the attacker has great computing power. The first major advantage of the proposed OTP-based method is that it only uses a single pre-shared key, The key is composed of two sections, a fixed number of bits followed by random bits, the size of each section is dependent on the robustness of the system. Analysis of the proposed technique shows that it provides perfect privacy by using a different key for each message to be encrypted. [ABSTRACT FROM AUTHOR]

The information theoretically secure Kirchhoff-law-Johnson-noise (KLJN) key exchange scheme, similarly to quantum key distribution (QKD), is also potentially vulnerable against clock attacks, where Eve takes over the control of clock synchronization in the channel. This short note aims to introduce a time synchronization protocol scheme for Alice and Bob, which is resistant against arbitrary time delay attacks, both symmetric and asymmetric ones. We propose and explore various ways of clock synchronization for the KLJN system and propose an ultimate protocol that preserves time and hardware integrity under arbitrary attacks. [ABSTRACT FROM AUTHOR]

A mutual authentication quantum key agreement protocol can authenticate participants' identities before establishing shared keys fairly. Therefore, it is more in line with the actual demand than the general quantum key agreement protocols. With Bell states and their entanglement exchange relations, a new mutual authentication quantum key agreement protocol is proposed. The participants can mutually authenticate each other's identity by using their secret identity information and the measurement correlation property of Bell states. Moreover, they can negotiate session keys fairly with the entanglement exchange relations of Bell states. The new mutual authentication quantum key agreement protocol is proved to be unconditionally secure and has good performance. [ABSTRACT FROM AUTHOR]

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This paper introduces and demonstrates four new statistical attacks against the Kirchhoff-Law-Johnson-Noise (KLJN) secure key exchange scheme. The attacks utilize compromised random number generators (RNGs) at Alice's/Bob's site(s). The case of partial correlations between Alice's/Bob's and Eve's probing noises is explored, that is, Eve's knowledge of Alice's and Bob's noises is limited but not zero. We explore the bilateral situation where Eve has partial knowledge of Alice's and Bob's RNGs. It is shown that in this situation Eve can crack the secure key bit by taking the highest cross-correlation between her probing noises and the measured voltage noise in the wire. She can also crack the secure key bit by taking the highest cross-correlation between her noise voltages and her evaluation of Alice's/Bob's noise voltages. We then explore the unilateral situation in which Eve has partial knowledge of only Alice's RNG thus only those noises (of Alice and Eve) are correlated. In this situation, Eve can still crack the secure key bit, but for sufficiently low error probability, she needs to use the whole bit exchange period for the attack. The security of the KLJN key exchange scheme, similarly to other protocols, necessitates that the RNG outputs are truly random for Eve. [ABSTRACT FROM AUTHOR]

Copyright of Journal of Railway Science & Engineering is the property of Journal of Railway Science & Engineering Editorial Office and its content may not be copied or emailed to multiple sites or posted to a listserv without the copyright holder's express written permission. However, users may print, download, or email articles for individual use. This abstract may be abridged. No warranty is given about the accuracy of the copy. Users should refer to the original published version of the material for the full abstract. (Copyright applies to all Abstracts.)

Based on single-particle states and four-particle GHZ states, a mutual authentication quantum key agreement protocol is proposed. The quantum key agreement protocol can not only establish shared keys fairly, but also authenticate participants’ identities before negotiating keys. In order to mutually authenticate each other’s identity, the verifier can identify the identity of the prover according to whether the prover can choose the correct measurement bases with the hash values of their shared secret identity information and the random number. In key agreement stage, two parties can fairly establish a shared key by using the measurement correlation property of four-particle GHZ states. The shared key involves the partial keys of two participants, their identity information and the values of two random numbers. Although the hash functions are used in both the mutual authentication stage and the key agreement stage, the new quantum key agreement protocol is still proved to be unconditionally secure. Moreover, it has flexible qubit efficiency and can achieve high qubit efficiency. [ABSTRACT FROM AUTHOR]

This paper introduces a new attack against the Kirchhoff–Law–Johnson-Noise (KLJN) secure key exchange scheme. The attack is based on the nonlinearity of the noise generators. We explore the effect of total distortion (TD) at the second order ( D 2 ), third order ( D 3 ) and a combination of the second and third orders ( D 2 , 3 ) on the security of the KLJN scheme. It is demonstrated that as little as 1% results in a notable power flow along the information channel, which leads to a significant information leak. We also show that decreasing the effective temperature (that is, the wire voltage) and, in this way reducing nonlinearity, results in the KLJN scheme approaching perfect security. [ABSTRACT FROM AUTHOR]

Realizing fundamental cryptographic primitives with unconditional security is a central topic in information-theoretic cryptography. These primitives can be realized based on physical assumptions, such as the existence of noisy channels, an upper bound on the storage capacity, or the laws of quantum mechanics. Palmieri and Pereira [1] demonstrated that delays in communication channels can be used as a reasonable and effective assumption to obtain an unconditionally secure oblivious transfer protocol against honest-but-curious adversaries. While any oblivious transfer protocol secure against malicious adversaries can be used to implement commitment, the reduction does not work if the oblivious transfer protocol is only secure against honest-but-curious adversaries. Thus, the question of obtaining a secure commitment protocol based on channel delays is still open. In this paper, we provide a concrete protocol for implementing string commitments based on packet reordering – a consequence of channel delays in packet networks.

Recently, several passive and active attack methods have been proposed against the Kirchhoff–Law–Johnson–Noise (KLJN) secure key exchange scheme by utilizing direct (DC) loop currents. The DC current attacks are relatively easy, but their practical importance is low. On the other hand, parasitic alternating (AC) currents are virtually omnipresent in wire-based systems. Such situations exist due to AC ground loops and electromagnetic interference (EMI). However, utilizing AC currents for attacks is a harder problem. Here, we introduce and demonstrate AC current attacks in various frequency ranges. The attacks exploit a parasitic/periodic AC voltage-source at either Alice's or Bob's end. In the low-frequency case, the procedure is the generalized form of the former DC ground-loop-based attack. In the high-frequency case, the power density spectrum of the wire voltage is utilized. The attack is demonstrated in both the low and the high-frequency situations. Defense protocols against the attack are also discussed. [ABSTRACT FROM AUTHOR]

This paper demonstrates the vulnerability of the Kirchhoff-Law-Johnson-Noise (KLJN) secure key exchanger to compromised random number generator(s) even if these random numbers are used solely to generate the noises emulating the Johnson noise of Alice's and Bob's resistors. The attacks shown are deterministic in the sense that Eve's knowledge of Alice's and/or Bob's random numbers is basically deterministic. Moreover, no statistical evaluation is needed, except for rarely occurring events of negligible, random waiting time and verification time. We explore two situations. In the first case, Eve knows both Alice's and Bob's random noises. We show that, in this situation, Eve can quickly crack the secure key bit by using Ohm's Law. In the other situation, Eve knows only Bob's random noise. Then Eve first can learn Bob's resistance value by using Ohm's Law. Therefore, she will have the same knowledge as Bob, thus at the end of the bit exchange period, she will know Alice's bit. [ABSTRACT FROM AUTHOR]

A new attack against the Kirchhoff-Law-Johnson-Noise (KLJN) secure key distribution system is studied with unknown parasitic DC-voltage sources at both Alice’s and Bob’s ends. This paper is the generalization of our earlier investigation with a single-end parasitic source. Under the assumption that Eve does not know the values of the parasitic sources, a new attack, utilizing the current generated by the parasitic dc-voltage sources, is introduced. The attack is mathematically analyzed and demonstrated by computer simulations. Simple defense methods against the attack are shown. The earlier defense method based solely on the comparison of current/voltage data at Alice’s and Bob’s terminals is useless here since the wire currents and voltages are equal at both ends. However, the more expensive version of the earlier defense method, which is based on in-situ system simulation and comparison with measurements, works efficiently.

According to the peculiar entanglement and measurement properties of the three-particle GHZ state, we have systematically analyzed that two GHZ states and three GHZ states satisfy some expressions after exchanging one or two groups of particles respectively, which are described as four interesting and flexible equations. The four equations can deduce that four GHZ states or even m GHZ states still satisfy some expressions after exchanging one group and two groups of particles, and they can be summarized as two general flexible equations. Furthermore, we also investigate their application in the field of quantum key agreement based on these equations. In particular, we combine with decoy photons to propose a novel session key sharing protocol, which can guarantee the unconditional security of the protocol. It is feasible to use the existing quantum processing technology to realize the proposed protocol. [ABSTRACT FROM AUTHOR]

We introduce relativistic multi-party biased die-rolling protocols, generalizing coin flipping to M≥2 parties and to N≥2 outcomes for any chosen outcome biases and show them unconditionally secure. Our results prove that the most general random secure multi-party computation, where all parties receive the output and there is no secret input by any party, can be implemented with unconditional security. Our protocols extend Kent's (Kent A. 1999 Phys. Rev. Lett.83, 5382) two-party unbiased coin-flipping protocol, do not require any quantum communication, are practical to implement with current technology and to our knowledge are the first multi-party relativistic cryptographic protocols. [ABSTRACT FROM AUTHOR]

Blockchain technology represented by Bitcoin and Ethereum has been deeply developed and widely used due to its broad application prospects such as digital currency and IoT. However, the security of the existing blockchain technologies built on the classical cryptography depends on the computational complexity problem. With the enhancement of the attackers' computing power, especially the upcoming quantum computers, this kind of security is seriously threatened. Based on quantum hash, quantum SWAP test and quantum teleportation, a quantum blockchain system is proposed with quantum secure communication. In classical cryptographic theory sense, the security of this system is unconditional since it has nothing to do with the attackers' computing power and computing resources. [ABSTRACT FROM AUTHOR]

This study addresses a new question regarding the security of the Kirchhoff-Law-Johnson-Noise (KLJN) scheme compromised by DC sources at Alice and Bob: What is the impact of these parasitic sources on active attacks, such as the man-in-the-middle (MITM) attack, or the current injection attack if Alice and Bod did not eliminate these sources? The surprising answer is that the parasitic DC sources actually increase the security of the system because, in the case of the MITM attack, they make easier to uncover the eavesdropping than the ideal situation. In some of the cases, Eve can fix this deficiency but then the problem gets reduced to the original MITM attack to which the KLJN scheme is immune, it is already proven earlier. [ABSTRACT FROM AUTHOR]

A quantum key distribution (QKD) network is proposed to allow QKD protocols to be the infrastructure of the Internet for distributing unconditional security keys instead of existing public-key cryptography based on computationally complex mathematical problems. Numerous countries and research institutes have invested enormous resources to execute correlation studies on QKD networks. Thus, in this study, we surveyed existing QKD network studies and practical field experiments to summarize the research results (e.g., type and architecture of QKD networks, key generating rate, maximum communication distance, and routing protocol). Furthermore, we highlight the three challenges and future research issues in the security of QKD networks and then provide some feasible resolution strategies for these challenges. [ABSTRACT FROM AUTHOR]

In (Nature) Science Report 5 (2015) 13653, Vadai, Mingesz and Gingl (VMG) introduce a new Kirchhoff-law-Johnson-noise (KLJN) secure key exchanger that operates with 4 arbitrary resistors (instead of 2 arbitrary resistance values forming 2 identical resistor pairs in the original system). They state that in this new, VMG-KLJN, non-equilibrium system with nonzero power flow, the security during the exchange of the two (HL and LH) bit values is as strong as in the original KLJN scheme. Moreover, they claim that, at practical conditions, their VMG-KLJN protocol "supports more robust protection against attacks". First, we investigate the power flow and thermal equilibrium issues of the VMG-KLJN system with 4 arbitrary resistors. Then we introduce a new KLJN protocol that allows the arbitrary choice of 3 resistors from the 4, while it still operates with zero power flow during the exchange of single bits by utilizing a specific value of the 4th resistor and a binary temperature set for the exchanged (HL and LH) bit values. Then we show that, in general, the KLJN schemes with more than 2 arbitrary resistors (including our new protocol mentioned above) are prone to 4 new passive attacks utilizing the parasitic capacitance and inductance in the cable, while the original KLJN scheme is naturally immune against these new attacks. The core of the security vulnerability exploited by these attacks is the different line resistances in the HL and LH cases. Therefore, on the contrary of the statement and claim cited above, the practical VMG-KLJN system is less secure than the original KLJN scheme. We introduce another 2, modified, non-equilibrium KLJN systems to eliminate the vulnerability against some - but not all - of these attacks. However the price for that is the loss of arbitrariness of the selection of the 4th resistor and the information leak still remains greater than zero. [ABSTRACT FROM AUTHOR]

Based on the fact that there is no secure E-payment system for direct transactions between banks, an improved inter-bank quantum E-payment system has been built. By taking advantage of good entanglement properties of the four-particle Cluster state and the unique measurement rules, our system cannot only support the unconditional security of E-payment, but also guarantee the blindness of the purchase information. Besides, our system also satisfies the properties of undeniability and unforgeability. [ABSTRACT FROM AUTHOR]

A quantum key distribution (QKD) network is proposed to allow QKD protocols to be the infrastructure of the Internet for distributing unconditional security keys instead of existing public-key cryptography based on computationally complex mathematical problems. Numerous countries and research institutes have invested enormous resources to execute correlation studies on QKD networks. Thus, in this study, we surveyed existing QKD network studies and practical field experiments to summarize the research results (e.g., type and architecture of QKD networks, key generating rate, maximum communication distance, and routing protocol). Furthermore, we highlight the three challenges and future research issues in the security of QKD networks and then provide some feasible resolution strategies for these challenges.